[PATCH v2 02/18] PCI: endpoint: Introduce pci_epc_map_align()
Kishon Vijay Abraham I
kvijayab at amd.com
Wed Apr 3 05:33:25 PDT 2024
Hi Damien,
On 3/30/2024 9:49 AM, Damien Le Moal wrote:
> Some endpoint controllers have requirements on the alignment of the
> controller physical memory address that must be used to map a RC PCI
> address region. For instance, the rockchip endpoint controller uses
> at most the lower 20 bits of a physical memory address region as the
> lower bits of an RC PCI address. For mapping a PCI address region of
> size bytes starting from pci_addr, the exact number of address bits
> used is the number of address bits changing in the address range
> [pci_addr..pci_addr + size - 1].
>
> For this example, this creates the following constraints:
> 1) The offset into the controller physical memory allocated for a
> mapping depends on the mapping size *and* the starting PCI address
> for the mapping.
> 2) A mapping size cannot exceed the controller windows size (1MB) minus
> the offset needed into the allocated physical memory, which can end
> up being a smaller size than the desired mapping size.
>
> Handling these constraints independently of the controller being used in
> a PCI EP function driver is not possible with the current EPC API as
> it only provides the ->align field in struct pci_epc_features.
> Furthermore, this alignment is static and does not depend on a mapping
> pci address and size.
>
> Solve this by introducing the function pci_epc_map_align() and the
> endpoint controller operation ->map_align to allow endpoint function
> drivers to obtain the size and the offset into a controller address
> region that must be used to map an RC PCI address region. The size
> of the physical address region provided by pci_epc_map_align() can then
> be used as the size argument for the function pci_epc_mem_alloc_addr().
> The offset into the allocated controller memory can be used to
> correctly handle data transfers. Of note is that pci_epc_map_align() may
> indicate upon return a mapping size that is smaller (but not 0) than the
> requested PCI address region size. For such case, an endpoint function
> driver must handle data transfers in fragments.
>
> The controller operation ->map_align is optional: controllers that do
> not have any address alignment constraints for mapping a RC PCI address
> region do not need to implement this operation. For such controllers,
> pci_epc_map_align() always returns the mapping size as equal
> to the requested size and an offset equal to 0.
>
> The structure pci_epc_map is introduced to represent a mapping start PCI
> address, size and the size and offset into the controller memory needed
> for mapping the PCI address region.
>
> Signed-off-by: Damien Le Moal <dlemoal at kernel.org>
> ---
> drivers/pci/endpoint/pci-epc-core.c | 66 +++++++++++++++++++++++++++++
> include/linux/pci-epc.h | 33 +++++++++++++++
> 2 files changed, 99 insertions(+)
>
> diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
> index 754afd115bbd..37758ca91d7f 100644
> --- a/drivers/pci/endpoint/pci-epc-core.c
> +++ b/drivers/pci/endpoint/pci-epc-core.c
> @@ -433,6 +433,72 @@ void pci_epc_unmap_addr(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> }
> EXPORT_SYMBOL_GPL(pci_epc_unmap_addr);
>
> +/**
> + * pci_epc_map_align() - Get the offset into and the size of a controller memory
> + * address region needed to map a RC PCI address region
> + * @epc: the EPC device on which address is allocated
> + * @func_no: the physical endpoint function number in the EPC device
> + * @vfunc_no: the virtual endpoint function number in the physical function
> + * @pci_addr: PCI address to which the physical address should be mapped
> + * @size: the size of the mapping starting from @pci_addr
> + * @map: populate here the actual size and offset into the controller memory
> + * that must be allocated for the mapping
> + *
> + * Invoke the controller map_align operation to obtain the size and the offset
> + * into a controller address region that must be allocated to map @size
> + * bytes of the RC PCI address space starting from @pci_addr.
> + *
> + * The size of the mapping that can be handled by the controller is indicated
> + * using the pci_size field of @map. This size may be smaller than the requested
> + * @size. In such case, the function driver must handle the mapping using
> + * several fragments. The offset into the controller memory for the effective
> + * mapping of the @pci_addr.. at pci_addr+@map->pci_size address range is indicated
> + * using the map_ofst field of @map.
> + */
> +int pci_epc_map_align(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> + u64 pci_addr, size_t size, struct pci_epc_map *map)
> +{
> + const struct pci_epc_features *features;
> + size_t mask;
> + int ret;
> +
> + if (!pci_epc_function_is_valid(epc, func_no, vfunc_no))
> + return -EINVAL;
> +
> + if (!size || !map)
> + return -EINVAL;
> +
> + memset(map, 0, sizeof(*map));
> + map->pci_addr = pci_addr;
> + map->pci_size = size;
> +
> + if (epc->ops->map_align) {
> + mutex_lock(&epc->lock);
> + ret = epc->ops->map_align(epc, func_no, vfunc_no, map);
> + mutex_unlock(&epc->lock);
> + return ret;
> + }
> +
> + /*
> + * Assume a fixed alignment constraint as specified by the controller
> + * features.
> + */
> + features = pci_epc_get_features(epc, func_no, vfunc_no);
> + if (!features || !features->align) {
> + map->map_pci_addr = pci_addr;
> + map->map_size = size;
> + map->map_ofst = 0;
> + }
The 'align' of pci_epc_features was initially added only to address the
inbound ATU constraints. This is also added as comment in [1]. The PCI
address restrictions (only fixed alignment constraint) were handled by
the host side driver and depends on the connected endpoint device
(atleast it was like that for pci_endpoint_test.c [2]).
So pci-epf-test.c used the 'align' in pci_epc_features only as part of
pci_epf_alloc_space().
Though I have abused 'align' of pci_epc_features in pci-epf-ntb.c using
it out of pci_epf_alloc_space(), I think we should keep the 'align' of
pci_epc_features only within pci_epf_alloc_space() and controllers with
any PCI address restrictions to implement ->map_align(). This could as
well be done in a phased manner to let controllers implement
->map_align() and then remove using pci_epc_features in
pci_epc_map_align(). Let me know what you think?
Thanks,
Kishon
[1] ->
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/pci-epc.h?h=v6.9-rc2#n187
[2] ->
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/misc/pci_endpoint_test.c?h=v6.9-rc2#n127
> +
> + mask = features->align - 1;
> + map->map_pci_addr = map->pci_addr & ~mask;
> + map->map_ofst = map->pci_addr & mask;
> + map->map_size = ALIGN(map->map_ofst + map->pci_size, features->align);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(pci_epc_map_align);
> +
> /**
> * pci_epc_map_addr() - map CPU address to PCI address
> * @epc: the EPC device on which address is allocated
> diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
> index cc2f70d061c8..8cfb4aaf2628 100644
> --- a/include/linux/pci-epc.h
> +++ b/include/linux/pci-epc.h
> @@ -32,11 +32,40 @@ pci_epc_interface_string(enum pci_epc_interface_type type)
> }
> }
>
> +/**
> + * struct pci_epc_map - information about EPC memory for mapping a RC PCI
> + * address range
> + * @pci_addr: start address of the RC PCI address range to map
> + * @pci_size: size of the RC PCI address range to map
> + * @map_pci_addr: RC PCI address used as the first address mapped
> + * @map_size: size of the controller memory needed for the mapping
> + * @map_ofst: offset into the controller memory needed for the mapping
> + * @phys_base: base physical address of the allocated EPC memory
> + * @phys_addr: physical address at which @pci_addr is mapped
> + * @virt_base: base virtual address of the allocated EPC memory
> + * @virt_addr: virtual address at which @pci_addr is mapped
> + */
> +struct pci_epc_map {
> + phys_addr_t pci_addr;
> + size_t pci_size;
> +
> + phys_addr_t map_pci_addr;
> + size_t map_size;
> + phys_addr_t map_ofst;
> +
> + phys_addr_t phys_base;
> + phys_addr_t phys_addr;
> + void __iomem *virt_base;
> + void __iomem *virt_addr;
> +};
> +
> /**
> * struct pci_epc_ops - set of function pointers for performing EPC operations
> * @write_header: ops to populate configuration space header
> * @set_bar: ops to configure the BAR
> * @clear_bar: ops to reset the BAR
> + * @map_align: operation to get the size and offset into a controller memory
> + * window needed to map an RC PCI address region
> * @map_addr: ops to map CPU address to PCI address
> * @unmap_addr: ops to unmap CPU address and PCI address
> * @set_msi: ops to set the requested number of MSI interrupts in the MSI
> @@ -61,6 +90,8 @@ struct pci_epc_ops {
> struct pci_epf_bar *epf_bar);
> void (*clear_bar)(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> struct pci_epf_bar *epf_bar);
> + int (*map_align)(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> + struct pci_epc_map *map);
> int (*map_addr)(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> phys_addr_t addr, u64 pci_addr, size_t size);
> void (*unmap_addr)(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> @@ -234,6 +265,8 @@ int pci_epc_set_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> struct pci_epf_bar *epf_bar);
> void pci_epc_clear_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> struct pci_epf_bar *epf_bar);
> +int pci_epc_map_align(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> + u64 pci_addr, size_t size, struct pci_epc_map *map);
> int pci_epc_map_addr(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> phys_addr_t phys_addr,
> u64 pci_addr, size_t size);
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